It is the sense of knowing where your body part is in space and proprioception occurs subconsciously. 

This can be impaired when joints are injured, such as with ligament sprains.

You may experience an unstable sensation of the joint. Your joint may even give-out.

This exercise as shown in the picture is one of the basic proprioception exercises one would start with after injuring your ankle.

A physiotherapist can help prescribe the correct exercises to improve your proprioception.